mirror of https://github.com/proxmox/mirror_qemu
ppc/kvm: Skip writing DPDES back when in run time state
On POWER8 systems the Directed Privileged Door-bell Exception State register (DPDES) stores doorbell pending status, one bit per a thread of a core, set by "msgsndp" instruction. The register is shared among threads of the same core and KVM on POWER9 emulates it in a similar way (POWER9 does not have DPDES). DPDES is shared but QEMU assumes all SPRs are per thread so the only safe way to write DPDES back to VCPU before running a guest is doing so while all threads are pulled out of the guest so DPDES cannot change. There is only one situation when this condition is met: incoming migration when all threads are stopped. Otherwise any QEMU HMP/QMP command causing kvm_arch_put_registers() (for example printing registers or dumping memory) can clobber DPDES in a race with other vcpu threads. This changes DPDES handling so it is not written to KVM at runtime. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Message-Id: <20190923084110.34643-1-aik@ozlabs.ru> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>master
parent
5c94dd3806
commit
972bd57689
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@ -993,6 +993,10 @@ int kvm_arch_put_registers(CPUState *cs, int level)
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}
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kvm_set_one_reg(cs, KVM_REG_PPC_TB_OFFSET, &env->tb_env->tb_offset);
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if (level > KVM_PUT_RUNTIME_STATE) {
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kvm_put_one_spr(cs, KVM_REG_PPC_DPDES, SPR_DPDES);
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}
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#endif /* TARGET_PPC64 */
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}
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@ -1297,6 +1301,7 @@ int kvm_arch_get_registers(CPUState *cs)
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}
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kvm_get_one_reg(cs, KVM_REG_PPC_TB_OFFSET, &env->tb_env->tb_offset);
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kvm_get_one_spr(cs, KVM_REG_PPC_DPDES, SPR_DPDES);
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#endif
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}
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@ -8200,11 +8200,10 @@ static void gen_spr_power8_dpdes(CPUPPCState *env)
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{
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#if !defined(CONFIG_USER_ONLY)
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/* Directed Privileged Door-bell Exception State, used for IPI */
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spr_register_kvm_hv(env, SPR_DPDES, "DPDES",
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SPR_NOACCESS, SPR_NOACCESS,
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&spr_read_generic, SPR_NOACCESS,
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&spr_read_generic, &spr_write_generic,
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KVM_REG_PPC_DPDES, 0x00000000);
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spr_register(env, SPR_DPDES, "DPDES",
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SPR_NOACCESS, SPR_NOACCESS,
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&spr_read_generic, SPR_NOACCESS,
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0x00000000);
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#endif
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}
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